1. Field of the Invention
This invention relates to an interlock assembly for a pair of circuit breakers and, more specifically, to an interlock assembly having a self retaining sliding bar mechanism which allows an operator to use both hands to toggle the breaker.
2. Background Information
There are a number of applications where it is required that the operation of two circuit breakers be coordinated such that only one circuit breaker can be in the closed, operating position at one time. For example, the operation of two circuit breakers must be coordinated when providing a power-consuming load with electrical power from either of two different sources, such as a commercial power system and an auxiliary supply. It is imperative in such applications that only one circuit breaker be in the closed, operating position at one time. A device that prevents both circuit breakers from being in the operating position is called an interlock.
Circuit breaker interlocks are known which couple the actuating means, for example, operating handles, of circuit breakers whose operation is to be coordinated. One common type of interlock assembly, such as is described in, for example, U.S. Pat. No. 6,043,439, utilizes a sliding bar that moves between a position wherein a first circuit breaker handle is blocked and a second circuit breaker handle is free to move and a position wherein the first circuit breaker handle is free to move and the second circuit breaker handle is blocked.
In many industrial applications, circuit breakers are mounted in a vertical relationship with respect to one another wherein one circuit breaker is mounted and stacked above the other circuit breaker. In such a configuration, the actuating mechanism, such as an operating handle, of each circuit breaker travels in a horizontal direction (perpendicular to the vertical orientation of the circuit breakers) from a closed position on a first side of the circuit breaker to an open position on a second side of the circuit breaker that is opposite the first side. In circuit breaker pairs that are oriented in this manner that utilize a sliding bar interlock assembly, the sliding bar will slide in the vertical direction to selectively block either the actuating mechanism of the top circuit breaker or the actuating mechanism of the bottom circuit beaker.
Thus, if the top circuit breaker in such a pair is in a closed condition (actuating mechanism positioned on the first side), the bottom circuit breaker in the pair will be in an open condition (actuating mechanism positioned on the second side), and the sliding bar will block the movement of the actuating mechanism of the bottom circuit breaker, thereby preventing it from changing from an open condition to a closed condition. In addition, the actuating mechanism of the top circuit breaker, when so positioned on the first side, will block the sliding bar and prevent it from sliding upward. The sliding bar will not be able to slide unless and until the actuating mechanism of the top circuit breaker is moved to the second side (open condition), which is out of the way of the path of the sliding bar. Thus, if an operator wants to toggle the circuit breakers so as to move the top circuit breaker to an open condition and the bottom circuit breaker to a closed condition, the operator must move the actuating mechanism of the top circuit breaker to the second side where it will be out of the way of the sliding bar, slide the sliding bar up and out of the way of the actuating means of the bottom circuit breaker, and move the actuating mechanism of the bottom circuit breaker to the first side where it blocks movement of the sliding bar. These steps are made difficult by the fact that gravity will force the sliding bar downward if not held in place by the operator. Thus, the operator must hold the sliding bar up with one hand and move the actuating mechanism of the bottom circuit breaker to the first side with the other hand. With larger circuit breakers that require higher forces to move the actuating mechanisms, this may be very difficult. Thus, there is a need for a sliding bar interlock assembly for a pair of circuit breakers that allows both hands of the operator to be free when moving the circuit breaker actuating mechanisms.